1. Field of the Invention
This invention relates to a coordinate input apparatus, and more particularly, to a wireless vibrating input pen and a coordinate input apparatus which detects a coordinate of an input point of vibration from the vibrating pen by detecting an elastic-wave vibration input from the vibrating pen by a plurality of sensors provided on a vibration transmitting plate.
2. Description of the Related Art
As apparatuses for inputting hand-written characters, figures and the like into processing apparatuses, such as computers and the like, coordinate input apparatuses using various kinds of input pens, tablets and the like have been known. In these kinds of apparatuses, image information consisting of input characters, figures and the like is displayed on display units, such as CRT displays and the like, or output to recorders, such as printers and the like. As methods of detecting a coordinate in tablet-type coordinate input apparatuses, the following methods have been known:
(1) A method in which an apparatus has a resistive film and a sheet material facing it, and the value of the coordinate of a pressed point is detected by a change in the resistance value of the point.
(2) A method in which the position of the coordinate is detected utilizing an electromagnetic or electrostatic induction between conductive sheets or the like facing each other.
(3) A method in which the position of the coordinate of an input pen is detected utilizing an ultrasonic vibration transmitted from the input pen to a tablet.
However, conventional coordinate input apparatuses adopting the above-described methods have the following disadvantages:
That is, in the above-described method using a resistive film (case (1)), since uniformity in a resistor directly influences accuracy in the input of a figure, a resistor having extremely high uniformity is needed. As a result, the resistor becomes very expensive. In addition, since two resistive films, that is, one for the x coordinate and the other for the y coordinate, are needed, transparency of a coordinate input surface is reduced. As a result, when, for example, the input surface is used superposed on an original or the like, the surface of the original becomes illegible.
Second, in the method utilizing electromagnetic induction (case (2)), since electric wires are arranged in the form of a matrix, a coordinate input surface is not transparent, and so is unsuitable to be used superposed on an original, a display unit, or the like.
Third, in conventional coordinate input apparatuses utilizing ultrasonic waves (case (3)), a method of detecting a delay time until the vibration generated by the input pen propagates within a propagation medium and reaches a transducer has been used. In this method, it is necessary to know a time to be used as a reference for detecting the delay time (for example, a time when the vibration is generated by the input pen). Accordingly, it has been necessary to continuously input information regarding the time when the vibration is generated by the input pen to a circuit for detecting a transmission delay time. Hence, the input pen for generating vibration must have been connected to the main body via a cable or the like. As a result, when characters, figures and the like are input using such a coordinate input apparatus, operability is reduced. Furthermore, when a signal from the apparatus is transmitted using radio waves or the like, the pen must incorporate a trasmitter and the like. Hence, it has been difficult to realize the same shape, weight and operability as those of a normal writing tool. However, if the above-described problems in the ultrasonic method were solved, the ultrasonic method would be able to provide a low-cost apparatus, since this method does not have the above-described disadvantages of the other methods, and provides a relatively simple mechanical structure.